This thesis is arguably the first extensive academic study of the controversial Northern Irish Presbyterian theologian James Ernest Davey (1890-1960). The thesis begins by introducing the reader to the biography of Davey and indicating why he is a significant figure in the Northern Irish context, before examining the limited literature that is available and exposing its weaknesses. After the Introduction the dissertation falls into two main parts, the first examining Davey's Trial for heresy (Chapters Three to Seven), the second considering Davey's theology apart from the Trial and as it appears in his writings, published and unpublished, (Chapter Eight). Part One opens, in Chapter Two, with a consideration of the context of the Heresy Trial, while Chapters Three to Seven discuss the individual charges of heresy levelled against Davey. In each of these chapters we examine the theological doctrine that was the subject of dispute between Davey and his theological adversaries, namely, Imputation, Person of Christ, Scripture, God and Sin, and Trinity. Our discussion of the individual charges enables us to come to a preliminary conclusion concerning to what extent, if any, the charges against Davey were justified, but it also provides us with the basis upon which we can begin to identify Davey's own distinctive theological position. The second part of the thesis is devoted to a close reading of the central principle of Davey's theology, namely Christology, which we will take as a case-study to help us illustrate the strengths and weaknesses of Davey's theology and the legitimacy or illegitimacy of the charges of heresy that were laid against him. Christology has been chosen because it is the link between the various charges levelled against Davey at the Heresy Trial. Part Two of the thesis will enable us to answer the question whether Davey was a theological hero in the Northern Ireland context or a heretic, as his opponents claimed him to be. The conclusion of the thesis is that Davey played an important role in introducing a much needed liberal strand into Northern Irish Presbyterianism, but recognizes the way he sometimes formulated this theology laid him open to misunderstanding. The thesis ends with a reflection on the continued significance of Davey's theology today.